Summary Mesophilic Aeromonas strains express a single polar flagellum in all culture conditions and produce lateral flagella on solid media. Such hyperflagellated cells demonstrate increased adherence. Nine lateral flagella genes, lafA–U for Aeromonas hydrophila, and four Aeromonas caviae genes, lafA1, lafA2, lafB and fliU, were isolated. Mutant characterization, nucleotide and N‐terminal sequencing demonstrated that the A. hydrophila and A. caviae lateral flagellins were almost identical, but were distinct from their polar flagellum counterparts. The aeromonad lateral flagellins exhibited higher molecular masses on SDS–PAGE, and this aberrant migration was thought to result from post‐translational modification through glycosylation. Mutation of the Aeromonas lafB, lafS or both A. caviae lateral flagellins caused the loss of lateral flagella and a reduction in adherence and biofilm formation. Mutations in lafA1, lafA2, fliU or lafT resulted in strains that expressed lateral flagella, but had reduced adherence levels. Mutation of the lateral flagella loci did not affect polar flagellum synthesis, but the polarity of the transposon insertions on the A. hydrophila lafT/U genes resulted in non‐motility. However, mutations that abolished polar flagellum production also inhibited lateral flagella expression. We conclude that Aeromonas lateral flagella: (i) play a role in adherence and biofilm formation; (ii) are distinct from the polar flagellum; (iii) synthesis is dependent upon the presence of a polar flagellum filament; and (iv) that the motor proteins of the polar and lateral flagella systems appear to be shared.

Reelin is a glycoprotein that is essential for the correct cytoarchitectonic organization of the developing CNS. Its function in the adult brain is less understood, although it has been proposed that Reelin is involved in signaling pathways linked to neurodegeneration. Here we analyzed Reelin expression in brains and cerebrospinal fluid (CSF) from Alzheimer's disease (AD) patients and nondemented controls. We found a 40% increase in the Reelin protein levels in the cortex of AD patients compared with controls. Similar increases were detected at the Reelin mRNA transcriptional level. This expression correlates with parallel increases in CSF but not in plasma samples. Next, we examined whether CSF Reelin levels were also altered in neurological diseases, including frontotemporal dementia, progressive supranuclear palsy, and Parkinson's disease. The Reelin 180-kDa band increased in all of the neurodegenerative disorders analyzed. Moreover, the 180-kDa Reelin levels correlated positively with Tau protein in CSF. Finally, we studied the pattern of Reelin glycosylation by using several lectins and the anti-HNK-1 antibody. Glycosylation differed in plasma and CSF. Furthermore, the pattern of Reelin lectin binding differed between the CSF of controls and in AD. Our results show that Reelin is up-regulated in the brain and CSF in several neurodegenerative diseases and that CSF and plasma Reelin have distinct cellular origins, thereby supporting that Reelin is involved in the pathogenesis of a number of neurodegenerative diseases.eelin is an extracellular 420-kDa glycoprotein that binds to the transmembrane receptors apolipoprotein receptor 2 and very-low-density lipoprotein receptor (1, 2), which transduce the Reelin signal through the intracellular adapter disabled-1 (3-5). Reelin signaling triggers a disabled-1-dependent signaling cascade involving several kinases, which ultimately controls proper neuronal migration and positioning during CNS development (for review see ref. 6).The complex pattern of Reelin expression is consistent with evidence that this protein has multiple roles in brain development and adult brain function (7-9). In the adult mammalian brain, Reelin has been proposed to influence synaptogenesis and neural plasticity and to favor memory formation (8)(9)(10)(11)(12). Reelin is also expressed in peripheral tissues, including the liver, and is detected in blood (10, 13). However, whether brain and other tissues contribute to the pool of Reelin in blood remains to be elucidated. In this context, we recently reported the presence of detectable levels of Reelin in adult cerebrospinal fluid (CSF) (14).Furthermore, the involvement of the Reelin signaling pathway in neurodegeneration has also been proposed (1,6,9,(15)(16)(17). First, Reelin binds to apolipoprotein E (ApoE) receptors, and some ApoE gene polymorphisms are considered risk factors for Alzheimer's disease (AD). Moreover, the lack of Reelin is associated with increased phosphorylation of Tau (1, 2, 18), whose hyperphosphorylation leads to intracel...

Normal physiologic functions of the cellular prion protein (PrPc) are still elusive. This GPI-anchored protein exerts many functions, including roles in neuron proliferation, neuroprotection or redox homeostasis. There are, however, conflicting data concerning its role in synaptic transmission. Although several studies report that PrPc participates in NMDA-mediated neurotransmission, parallel studies describe normal behavior of PrPc-mutant mice. Abnormal axon connections have been described in the dentate gyrus of the hippocampi of PrPc-deficient mice similar to those observed in epilepsy. A study indicates increased susceptibility to kainate (KA) in these mutant mice. We extend the observation of these studies by means of several histologic and biochemical analyses of KA-treated mice. PrPc-deficient mice showed increased sensitivity to KA-induced seizures in vivo and in vitro in organotypic slices. In addition, we show that this sensitivity is cell-specific because interference experiments to abolish PrPc expression increased susceptibility to KA in PrPc-expressing cells. We indicate a correlation of susceptibility to KA in cells lacking PrPc with the differential expression of GluR6 and GluR7 KA receptor subunits using real-time RT-PCR methods. These results indicate that PrPc exerts a neuroprotective role against KA-induced neurotoxicity, probably by regulating the expression of KA receptor subunits.

BackgroundPrionopathies are characterized by spongiform brain degeneration, myoclonia, dementia, and periodic electroencephalographic (EEG) disturbances. The hallmark of prioniopathies is the presence of an abnormal conformational isoform (PrPsc) of the natural cellular prion protein (PrPc) encoded by the Prnp gene. Although several roles have been attributed to PrPc, its putative functions in neuronal excitability are unknown. Although early studies of the behavior of Prnp knockout mice described minor changes, later studies report altered behavior. To date, most functional PrPc studies on synaptic plasticity have been performed in vitro. To our knowledge, only one electrophysiological study has been performed in vivo in anesthetized mice, by Curtis and coworkers. They reported no significant differences in paired-pulse facilitation or LTP in the CA1 region after Schaffer collateral/commissural pathway stimulation.Methodology/Principal FindingsHere we explore the role of PrPc expression in neurotransmission and neural excitability using wild-type, Prnp −/− and PrPc-overexpressing mice (Tg20 strain). By correlating histopathology with electrophysiology in living behaving mice, we demonstrate that both Prnp −/− mice but, more relevantly Tg20 mice show increased susceptibility to KA, leading to significant cell death in the hippocampus. This finding correlates with enhanced synaptic facilitation in paired-pulse experiments and hippocampal LTP in living behaving mutant mice. Gene expression profiling using Illumina™ microarrays and Ingenuity pathways analysis showed that 129 genes involved in canonical pathways such as Ubiquitination or Neurotransmission were co-regulated in Prnp −/− and Tg20 mice. Lastly, RT-qPCR of neurotransmission-related genes indicated that subunits of GABAA and AMPA-kainate receptors are co-regulated in both Prnp −/− and Tg20 mice.Conclusions/SignificancePresent results demonstrate that PrPc is necessary for the proper homeostatic functioning of hippocampal circuits, because of its relationships with GABAA and AMPA-Kainate neurotransmission. New PrPc functions have recently been described, which point to PrPc as a target for putative therapies in Alzheimer's disease. However, our results indicate that a “gain of function” strategy in Alzheimer's disease, or a “loss of function” in prionopathies, may impair PrPc function, with devastating effects. In conclusion, we believe that present data should be taken into account in the development of future therapies.